PHENOMENA OF INHERITANCE 



is graphically represented in Fig. 58 in 

 which X represents the sex-determiner, which 

 is duplex in the female and simplex in the 

 male, and the chance unions of male and fe- 

 male gametes yield females (XX) and males 

 (XO) in equal numbers. 

 In either sex many secondary sexual charac- 



Gametes 



Fi 



FIG. 58. Diagram showing sex as a Mendelian character, 

 the female being homozygous, the male heterozygous for sex. 

 The female forms gametes all of which contain the X 

 chromosome; the male forms two sorts of gametes one-half 

 of which contain the X chromosome and the other half lack 

 it. All possible combinations of these gametes give a 2:2 or 

 1:1 ratio of females to males. 



